JAKARTA, Indonesia — Villagers living on the Indonesian side of Borneo killed at least 750 endangered orangutans in a year, some to protect crops from being raided and others for their meat, a new survey shows.

Such practices, never before quantified, are now believed to be a more serious threat to the existence of the red apes than previously thought, Erik Meijaard, the main author of the report that appeared in the journal PLoSOne, said Monday.

Indonesia — home to 90 percent of the orangutans left in the wild — was blanketed with plush rain forests less than 50 years ago, but half those trees have since been cleared in the rush to supply the world with timber, pulp, paper and more recently, palm oil.

As a result, most of the remaining 50,000 to 60,000 apes live in scattered, degraded forests, putting them in frequent, and often deadly, conflict with humans.

"But our surveys also indicate that killing of orangutans is happening deep inside forested areas, where orangutans are hunted just like any other species," Meijaard said. "This may be an uncomfortable truth, but not one that we can any longer ignore."

The Nature Conservancy and 19 other private organizations, including the WWF and the Association of Indonesian Primate Experts and Observers, carried out the survey to get a better understanding of orangutan killings and their underlying causes.

They interviewed 6,983 people in 687 villages in three provinces of Kalimantan — the Indonesian side of Borneo, which is shared also with Malaysia and Brunei — between April 2008 and September 2009.

Figures from the interviews were extrapolated to the target population of men 15 years and older, since only 11 women reported killing orangutans. This indicated that at least 750 apes had been killed during the previous year.

Neil Makinuddin, program manager of The Nature Conservancy, said they were surprised how many respondents reported killing and then eating orangutans — just over half.

Some were consumed after being killed for entering crops or because people were afraid of the animals, the study showed. Others were hunted outright for their meat.

The authors were quick to stress, however, that the people who admitted to killing orangutans said they'd only done so once or twice over the course of their lives.

"Orangutans are not part of people's day-to-day diet," said Meijaard, a senior adviser for the People and Nature Consulting International.

Indonesian Forestry Ministry spokesman Ahmad Fauzi Masyhud said his office has not yet received the report, which he described as "bombastic."

"We have to recheck whether it is true or not," he said. "But frankly I doubt it."

But Meijaard said it's time to face up to the facts.

"We used robust scientific methods to assess the social dimensions of orangutan conservation," he said. "Unless we assume that most of the survey respondents lied, we have to accept the hunting issue as an uncomfortable truth that needs to be addressed if we want to save the orangutan."

He said he's seen far too many orangutan skulls, skins and chopped off hands, and heard too many firsthand accounts of people having killed or eaten orangutans, to believe it isn't happening.

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